Nurse her sister's baby? I was stunned. Apparently she did this quite often.

That's one reason, 14 years later, I was so intrigued when I heard about a new movement of women nursing each other's babies and sharing pumped breast milk.

Many of these women meet over the Internet, where Web sites such as craigslist.org and parent chat groups have made it easier for mothers to reach each other.

The practice is so prevalent that craigslist and La Leche League told my producer that they and many other Web sites regularly pull these postings out of fear of running afoul of some state laws against selling any bodily fluids.

I traveled to the Boston suburbs, Pittsburgh, upstate New York, and Lakeville, Minnesota to meet some of these women.

When Jenn Connell set up her Web site, feedmybaby.com, she never dreamed she'd get the response she did. Connell couldn't breast-feed her two sons -- she'd lost her breasts to cancer, but through the site found 35 women to donate milk -- most sharing pumped milk and a handful actually nursing her sons on occasion.

Cathy Lundgren has found six women to donate pumped breast milk to her baby, Hannah, whom she adopted from Guatemala. Her main supplier has been Jacqui Gilstrap, who shipped frozen milk to Lundgren in Lakeville, Minnesota, from her home in Pittsburgh, Pennsylvania.

I also met Kelley Faulkner, who lives outside Boston and who can't produce much breast milk on her own because of breast surgery she had years ago. Faulkner has found 20 women to donate pumped milk to her son, Loren.

Most of the women I met take great precautions when entering a milk-sharing agreement, having their donor moms fill out a health questionnaire, and requiring lab work showing they'd tested negative for diseases like HIV and hepatitis.

But the American Academy of Pediatrics and the La Leche League, an international parent group devoted to breast-feeding, frown upon this kind of milk sharing. They point out that even if someone tests negative for a disease, they could contract it after the testing while still supplying milk to the baby.

Yet, experts, and even formula makers, agree that breast milk is best and not everyone can produce enough of it.

It's the only perfect food for babies. It has antibodies and other properties that infant formula can't copy.

Study after study shows that breast-fed babies have all sorts of health advantages, such as fewer ear infections, a lower risk of developing asthma, and even higher IQ's.

The mothers I met were determined to find breast milk for their babies when they themselves were not, for whatever reason, able to lactate.

There's no way to know how many women participate in milk sharing, but just do a little Web surfing and you'll find many trying to donate, sell, or acquire someone else's breast milk -- and that doesn't even count the women quietly in their own homes nursing each others babies or giving pumped breast milk to a friend.

This milk-sharing movement, is to a large extent, powered by the Internet, where people can meet total strangers with amazing speed. It's gotten extra momentum from recommendations of the American Academy of Pediatrics. Even formula companies recommend breastfeeding instead.

But it's also copying something that existed long before cyberspace. For time immemorial, women have nursed their sisters' babies, or hired wet nurses.

So perhaps I shouldn't have been stunned when I met that mother in Mississippi 14 years ago.

Years after that meeting, when I had my own children, shared nursing actually made a lot more sense. It's not always easy to be the sole provider of nutrition to a baby, and imagine the convenience of having someone you trust to help provide your baby with the perfect beverage.